Treatment of hydrocarbon oils



C. O. HOOVER TREATMENT OF HYDROCARBON OILS Sept. 14, 1943.

Filed April 27, 1942 l INVENTOR O CHARLES O. HO OVER n: Ww/1M" n ATTORNEYS Patented Sept. 14, 1943 UNITED STATES PATENT OFFICE TREATMENT 0F HYDROCARBON OILS Charles 0. Hoover, Houston, Tex., assigner to Air Reduction Company, Incorporated, New York, N. Y., a corporation of New York Application April 27, 1942, Serial No. 440,716

15 Claims.

The invention relates to treating sour petroleum distillates, or sour hydrocarbon oils, such as kerosene, naphtha, gasoline and the like to sweeten them, and to the treatment of such oils and distillates for the purpose of removing corrosive agents, such as free sulphur. The distillates treated in accordance with the present invention may be derived either from naphthenic base crudes or paraflinic base crudes and may be straight run distillates, such as are obtained by direct distillation, without intentional cracking of the petroleum from which they are derived, or the distillates treated in accordance with the present invention may be derived from petroleum which has been subjected to a cracking operation. These distillates are respectively referred to in the art as straight run distillates, and cracked or pressure distillates.

Distillates produced from petroleum oil frequently contain organic sulphur compounds which impart a bad odor to the distillates. Distillates produced from petroleum are subjected to the well known doctor test. A distillate giving a positive doctor test is said to be soun whereas a distillate which gives a negative doctor test is said to be sweet A positive doctor test is due to the presence of organic sulphur compounds, principally mercaptans, in the discatalysts and in the absence of compounds of l metals the sulphides of which are insoluble in water solutions of a hydroxide of an alkali metal, and (2) an aqueous solution containing in dissolved condition (a) an alkali metal hydroxide, for example sodium hydroxide, (b) an alkali metal monosulphide, for example sodium monosulphide and (c) an alkali metal polysulphide, for example, a polysulphide of sodium. The total amount of combined sulphur in the form of alkali metal (e. g., sodium) monosulphide and alkali metal (e. g., sodium) polysulphide should be such as would correspond to or equal the total amount of sulphur in mixtures of alkali metal monosulphide (e. g., sodium monosulphide) with alkali metal disulphide (e. g., sodium disulphide) In other words the said aqueous solution corresponds with or is equivalent to a solution prepared by dissolving a mixture of alkali metal monosulphide (e. g., sodium monosulphide) and alkali metal disulphide (e. g., sodium disulphide) in the water in which the alkali metal hydroxide 4(e. g., sodium hydroxide) is dissolved. For convenience of reference inthis description and for the purpose of simplication of explanations hereinafter given the said aqueous solution is considered as containing in dissolved condition alkali metal monosulphide, alkali metal disulphide and alkali metal hydroxide.

The treatment of the oil with the uncombined oxygen and the alkali metal hydroxide, the alkali metal monosulphide and the alkali metal polysulphide should take place in the presence of a compound which will promote contact of the oil and the reagents which bring about a sweetening of the oil or distillate and the removal of corrosive agents therefrom. Soaps or salts of metals which form soluble sulphides have been found particularly effective in promoting such contact. While such soaps or salts, or contact-promoting-agents appear to take no direct part, either in the sweetening of the oil, or in the removal. of corrosive agents therefrom, it has been found that their presence is necessary if satisfactory sweetening and removal of corrosive agents are to be obtained. Accordingly the present invention contemplates the Icarrying out of the treatment of the oil in the presence of such soaps or salts, or contact-promoting-agents.

Bearing in mind the foregoing explanations in regard to the nature of the aqueous solution used in my process, the process of the present invention, briefly stated, consists in intimately contacting a water solution containing alkali metal hydroxide, alkali metal monosulphide and alkali metal disulphide with the sour petroleum distillate to be sweetened, such contact being performed in the presence of a soap or salt of a metal which forms sulphides which are soluble in aqueous solutions and in the absence of an oxidation catalyst and of a compound of a metal, the sulphide of which is insoluble in water solutions of an alkali metal hydroxide, while a regulatable stream of gaseous oxygen is introduced into the zone, chamber or vessel in which the sour petroleum distillate and the said solution are being contacted, the said oxygen being used at a rate or in amounts as hereinafter more fully appears.

The process has been practiced in a continuous manner by adding a stream of gaseous oxygen to a stream of sour petroleum distillate, and introducing this mixture as a stream into a mixing chamber into which the treating solution and the soap or salts also flow as a stream. In the mixing chamber, the petroleum distillate carrying the oxygen is intimately mixed and contacted with the treating solution, whereupon the mixture of distillate and solution flows as a stream into a settling chamber or a series of such chambers in which the solution and soap or salts settle from the mixture, the sweetened distillate continuously flowing from the settling chamber or chambers while the settled solution is continuously returned to the mixing chamber to be contacted with the oncoming sour petroleum distillate containing added oxygen. The rate of introducing the oxygen into the sour distillate is controlled by means of a valve in the pipe which conducts the oxygen into the sour distillate.

Although in the foregoing paragraphs I have indicated the absence of an oxidation catalyst and the absence of compounds of metals the sulphides of which are insoluble in aqueous solutions of alkali metal hydroxide, for example copper, nickel, iron, manganese, lead. etc., in the practice of my process, I do not mean to indicate thereby that those small amounts of oxidation catalysts and of the compounds of said metals which naturally or accidentally occur in the treating agents or chemicals used or in the pentroleum distillates treated must be excluded, but on the other hand, I mean that the process is practiced in the absence of a substantial quantity of an oxidation catalyst or of such a. compound of said metals, the intention being, in the preferred manner of practicing my invention, to exclude as much as possible the presence of oxidation catalysts and such compounds of said metals.

The process of the present invention is based upon my discovery that when a water solution containing dissolved alkali metal monosulphide (e. g., sodium monosulphide, NazS), alkali metal disulphide (e. g., sodium disulphide) and alkali metal hydroxide (e. g., sodium hydroxide) is intimately contacted with sour petroleum distillates, advantage may be taken of the property of alkali metal monosulphide (e. g., sodium monosulphide, NazS) to hydrolyze to bring about, in a controllable and regulatable manner, the sweetening of the sour petroleum distillate, by the action of gaseous (molecular) oxygen on said hydrolysis, whereby the course and rate of the sweetening action of the solution and the composition of the solution can be controlled and regulated by regulating or changing the rate of supply of gaseous (molecular) oxygen. The effect of the gaseous oxygen upon the said hydrolysis in my process is to produce alkali metal hydroxide and akali metal disulphide as fast as alkali metal hydroxide and alkali metal disulphide are consumed by the conversion of the mercaptans into organic disulphide, and except for the slow formation of sodium thiosulphate the treating solution would last, unchanged in composition, as long as oxygen is supplied to it. It is owing to this discovery that the necessity arises of excluding oxidation cata lysts and compounds of metals which might act as oxidation catalysts, since any enhancement of the oxidation powers of gaseous (molecular) oxygen would lead to an undesired increase in alkali thiosulphates produced. For similar reasons the use of compounds which yield nascent oxygen, such as peroxides and persalts, are excluded from my process. Further, the peroxidized compounds and persalts do not admit of simple and effective regulation as a stream of gaseous oxygen. The above more fully appears from the details, hereinafter given, of the chemical reactions involved.

In the explanations and description which follow, the mercaptans are represented generally by the chemical formula RSH, where R is an organic radical, containing, for example, carbon and hydrogen atoms.

When the water solution of sodium hydroxide, sodium monosulphide and sodium disulphide is intimately contacted or mixed with the sour petroleum distillates, the mercaptans are converted into organic disulphides according to the following chemical equations:

However, the addition of Equations 1 and 2 gives the same final equation as the addition of Equations 3 and 4, namely:

If the water is pure, and contains no substances affecting the equilibrium, the hydrolysis goes strongly towards the right of Equation 6, namely as follows:

(7) NazS-l-HzO-*NaHS-i-NaOI-I However, the sodium hydroxide which is in the treating solution initially provides` a high concentration of sodium hydroxide over and above that which is yielded by the hydrolysis according to Equation 6, and, therefore, the hydrolysis instead of proceeding towards the right of Equation 6 is forced back towards the left of Equation 6, namely as follows:

That is to say, the sodium monosulphide remains or largely remains as such (unhydrolyzed) in the treating solution.

According to my invention, I influence the equilibrium represented by Equation 6 to proceed towards the right in spite of the influence of the sodium hydroxide in the treating solution to influence it to proceed towards the left. That is to say I cause the hydrolysis to proceed according to Equation 7. This is done by the molecular or gaseous oxygen. The oxygen used in the sweetening process, or at least a part of it, reacts with sodium hydrosulphide as follows:

(9) NaHS+ 1/ Oz=NaOH-{S This reaction, therefore, causes the equilibrium molecules of NazS represented by Equation 6 to proceed towards the right, namely as follows:

As the reactions represented by Equations 10 and 9 take place simultaneously, the final chemical action of the two is obtained by adding Equations 9 and 10, which addition gives Now considering Equation which gives the sweetening reaction, it will be seen that two are produced in that reaction. One of these molecules of sodium monosulphide (NazS) is available for hydrolysis and oxidation according to Equation 11, whereby two molecules of sodium hydroxide which were consumed in the sweetening reaction of Equation 5 are regenerated. The other molecule of sodium monosulphide (NazS) produced in the reaction represented by Equation 5 is available for combining with the nascent sulphur produced in the reaction represented by Equation l1, which sulphur is the same sulphur produced in the reaction represented by Equation 9. This sulphur does not precipitate, but immediately combines with a molecule of sodium monosulphide (NazS) to form sodium disulphide (NazSz) according to the following equation:

whereby the sodium disulphide which is required for the sweetening reaction of Equation 5 is regenerated. Thus, the oxygenused in my process regenerates sodium hydroxide and sodium disulphide required in the chemical actions involved in the sweetening of the sour distillates. Since, however, the reactions represented by Equation 9 or `11 are accompanied by the formation o f some sodium thiosulphate or some other salt of an acid containing oxygen and sulphur, the latter will gradually accumulate during long periods of operation, and only after such long periods of time will it be found necessary to add more reagents to the treating solution or to substitute it by an entirely fresh solution.

For the purpose of further explaining the features of my process, Equations, l1 and 12, which represent the reactions of sweetening and of the effect of oxygen on the reagents in solution in the treating solution, are assembled here and added: v

(5) 2RSH+2NaOH+NazSz= RS-SR.-|2NazSi-2H2O Thus the chemistry of my process may be viewed as being the direct oxidation of the mercaptans by the gaseous oxygen through the agency of the solution of sodium monosulphide, sodium disulphide and sodium hydroxide; and this is substantiated in the commercial practice of my process by the fact that the rate or extent of sweetening of the petroleum to the process increases with increase of supply of oxygen and decreases with decrease of supply of oxygen. In the commercial application of my process, any slight or even great sourness of the treated oilis corrected by increasing the rate` of supplying the whole course and rate of the sweetening of the sour distillate can be controlled by controlling the rate at which oxygen is supplied, and -why oxidation catalysts and the use of peroxidized compounds and other compounds yielding nascent Oxygen are undesired. 'I'he use of oxidation catalysts and peroxidized compounds would unneces-- sarily hasten the production of thiosulphates, and further, peroxidized compounds, such as persalts a'nd peracids, would introduce foreign ions into the treating solution which would complicate the control of the equilibrium represented by Equation 6.

It will now also be appreciated from the above disclosures concerning my process that the'DreS- ence of compounds of metals the sulphides of which are insoluble in aqueous solutions of alkali metal hydroxide are disadvantageous because (1) many of the compounds are oxidation catalysts; (2) they would form suspensions of finely divided solid material in the treating solution used in my process and would produce diiilculties in separating the treated petroleum distillate from the treating solution and in obtaining a treated ,distillate free of suspended solid matter, particularly in a process operating upon a continuous flow or stream of sour petroleum distillate and in which the treating solution flows in a cycle; (3) the color stability of the treated petroleum distillate or the stability of the treated distillate as regards gum formation is adversely iniluenced my many of these compounds; and (4) further, some of these compounds cause or tend to cause the formation of organic polysulphides higher in sulphur content than organic disulphides.

From the foregoing it will also appear that increasing or decreasing the rate of supply of oxygen increases or decreases the rate of sweetening by the treating solution, and therefore regulating or changing the rate of feed or oxygen regulates or changes the rate of sweetening in the same direction. Regardless of the accuracy of the chemical reactions given above,'I have found it to be a fact in practicing the process of the present invention, that the sweetening action can be increased or decreased Aby respectively increasing or decreasing the rate of supply of oxygen. For example, if conditions arise during the practice of my process which cause the treated petroleum distillate to flow fromthe treating apparatus slightly sour, an increase in the rate of supply of oxygen will correct this condition and the treated distillate will then flow from the treating apparatus in sweet condition. The oxygen, as will appear from the explanations given,

distillatebeing subjected gaseous oxygen, whereupon the treated oil again ilows in sweet condition from v thetreating apparatus.

It will now appear evident how and why the produces both sodium disulphide and sodium hydroxide which are reagents required by the sweetening reaction of Equation 5.

Bearing in mind that both sodium monosulphide and sodium disulphide are reducing agents,

it is indeed surprising, without the explanations given above, that oxidation of mercaptans could be accomplished in their presence and that the rate of oxidation of the mercaptans can be respectively increased or decreased by increasing or decreasing the rate of supplying oxygen in the process.

A not inconsiderable feature of my invention also resides in the fact that the sour petroleum distillates which may be treated by my process may either contain elemental sulphur or hydro gen sulphide or both. In these events, the hydrogen sulphide will combine with some of the sodium hydroxide in the treating solution forming sodium monosulphide. and the sulphur will combine with some of the sodium monosulphide forming sodium disulphide. thereby removing hydrogen sulphide andy free (corrosion) sulphur` from the petroleum distillate. However, I prefer to remove the hydrogen sulphide, or the greater part of it, from the petroleum distillate before it is treated according to the present invention. Such removal of hydrogen sulphide from the petroleum distillate may be accomplished in any suitable manner, for example by intimately mixing or contacting the petroleum distillate with solid sodium hydroxide or with a Water solution of sodium hydroxide.

In my process, the alkali metal mercaptides of the lower mercaptans are susceptible to oxidation to organic disulphides even without the intervention of sodium disulphide, owing to the fact that alkali metal mercaptides of the lower mercaptans are oxidizable to organic disulphides by elementary oxygen. The fact that this oxidation can occur in my process in the presence of a reducing solution is also an important feature of my invention, in that autoxidized hydrocarbons, which may exist in the petroleum distillate, either before treatment or which may be formed therein by the oxygen during treatment, are converted into reduced form by the action of the solution.

The rate of.supplying gaseous oxygen in my process depends in general upon the sourness and um distillate. The greater the sourness of the petroleum distillate, theI more oxygen will be required. Sour petroleum distillates which contain free sulphur will require less oxygen for sweetening than they would have required if the free sulphur were not present, and this is due to the fact that the free sulphur reacts with a part of the sodium monosulphide to produce sodium disulphide which supplies a part of the sodium disulphide required by the sweetening reaction represented in Equation 5.

The gaseous oxygen which is used in the process may be (l) pure gaseous oxygen, (2) mixtures of gaseous oxygen and gaseous nitrogen which are richer in oxygen than the air of the atmosphere, or (3) atmospheric air. I have found that a mixture consisting of 99.5% oxygen and 0.5% nitrogen and inert constituents of the atmosphere is very satisfactory for use. 'The terms gaseous oxygen or oxygen in the appended claims are intended to include gaseous oxygen in the above indicated forms.

The process can be operated at atmospheric or climatic temperatures or at temperatures up to about 120 F. Temperatures above about 120 F. should not be used as above about that temperature sulphides will be formed which are of such a nature that they will not take up sulphur. Also, above about that temperature a, change takes place in the soap or salt which is present Which renders it less eiective in promoting contact between the oil or distillate and the sweetening reagents. Also, above 120 F. there is greater vaporization of the oil or distillate unless special precautions are taken to prevent vaporization. The pressure at which the treatment of the oil or distillate is carried out is not material. The treatment may take place at atmospheric pressure, or at a higher or lower pressure. I have already operated the process on plant or large scale on petroleum distillates at temperatures as low as 32 F., as well as on petroleum distillate at temperatures as high as 110 F.

Below are given examples of the manner in which my invention has been and is being practiced on a commercial scale.

Example I A sour petroleum naphtha of the following specifications was treated:

The solution used in treating `this naphtha was prepared from the following ingredients in the indicated proportions:

Pounds Water 1931 Flake sodium hydroxide 109'7 Fused sodium monosulphide 100 Flowers of sulphur 10 These ingredients were intimately mixed together at ordinary atmospheric temperatures to effect solution without the application of heat. 'I'he sulphur went into solution in the form of sodium l disulphide by reaction with a part of the sodium monosulphide. The ten pounds of sulphur require about 24 pounds of sodium monosulphide to convert them into sodium disulphide, leaving '76 pounds of sodium monosulphide. The ten pounds of sulphur and 24 pounds of sodium monosulphide would produce 34'pounds of'sodium disulphide. The treating solution, therefore contained after solution of the sulphur:

'Ihe agent used for promoting contact between the oil or distillate and the reagents for sweetening the oil and removing corrosive agents was sodium naphthenate.

Example II In a second example 60 parts of aviation gasoline were treated in the presence of sodium naphthenate and at atmospheric temperature and at atmospheric pressure with 40 parts of the reagent used in Example I, and the resulting mixture was agitated in the presence of pure oxygen for 30 minutes. The mixture was then permitted to settle for a period of 10 minutes and the gasoline which formed the supernatant liquor above the treating reagent was sweet and required no further treatment. The sodium naphthenate and the excess sodium hydroxide solution separated into two bright, clear layers, suitable for continued use in treatment of aviation gasoline or other oils or distillates.

Comparative tests before and after treating the aviation gasoline were as follows:

Copper Clear 3 cc. Total octane T. E. L. sulphur dgigg" Untreated 73.8 89.6 0.009 Peacock. Treated 75.9 93.4 0.007 Perfect.

utilized in treating the oil or solution is illustrated in the acin which the numerals I and 2 indicate settling drums each eighteen feet high and four feet in diameter. The numeral 3 indicates a reacting or mixing chamber ten feet high and six inches in diameter, provided with perforated mixing plates 4 equally spaced along the height of the mixing chamber. A pipe 5 leads from the top of mixing chamber 3 to settling chamber I and discharges therein at about four feet from the bottom thereof. A pipe 6 leads from the top of settling chamber I to near the bottom of settling chamber 2. Settling chamber 2 has an outlet pipe 1 at the top for conducting the treated oil or distillate to a pipe 1a having a valve 1b and leading to a storage tank 8. The bottom of the settling chamber I communicates with the bottom of the reacting chamber or mixer I by means of pipe 9 having a valve I0, pump II, and pipes I2 and I3.

'Ihe sour oil or distillate is supplied through a pipe I 4 which connects with the pipe I3 leading to the bottom of the reacting chamber 3. The gaseous oxygen is introduced into the sour oil or distillate flowing through the pipe I4 by means of a pipe I5 having a valve I6 for regulating the rate at which the gaseous oxygen is introduced. If desired, the gaseous oxygen may be introduced directly into the reacting chamber 3 n ear the bottom, instead of being introduced along with the naphtha, or it may be introduced into the reacting chamber between the two lowermost perforated mixing plates, or it may be introduced into the pipe I3 leading to the bottom of the reacting chamber.

A pump I1 is interposed in the sour oil or distillate supply line I4 for'supplying the oil or distillate at the desired rate. The oil or distillate supply line also has a valve I8 so that the supply of oil or distillate and oxygen to the reacting chamber may be further regulated or entirely cut oi.

The sodium naphthenate or other soap or salt may be prepared in a mixing tank I9 which is connected to the pipe 9 at the intake side of the pump I I by a pipe having a valve 2 I.

The settling chambers I and 2 are provided with drain-off pipes 22 and 23 having valves 24 and 25, respectively.

In preparing for operation, the valves I0, I8, 2|, 24 and 25 are closed and the solution of alkali metal hydroxide, alkali metal monosulphide and alkali metal polysulphide, as prepared above, is introduced into the bottom of the settling chamber I through the pipe 26, the valve 21 therein being open. When a sufficient amount of the solution has been introduced, the valve 21` is closed and valve 2| opened and the pump II started until enough of the soap or salt solution from the tank I9 has been pumped into the system. Valve 2| is then closed and valve I0 opened and the soap cr salt solution, the alkali metal hydroxide, the alkali metal monosulphide and the alkali metal polysulphide solution circulated until they have become intimately admixed. The total amount of the resulting mixture should be such that during operation it will stand about four feet in the settling chamber I. The amount of the soap or salt in the mixture should comprise about 25% to 50% thereof.

After the soap and the reaction solution have been thoroughly admixed, the valve I8 is opened and pump I1 started to cause the sour oil or distillate and oxygen from the pipe I4 to be intro- The apparatus distillate with the companying drawing,

duced into the reacting chamber 3 along with the reagent mixture. The pump II continues to operate and the reagent mixture and the sour oil or distillate and oxygen are caused to pass through the reacting chamber 3 where the sour oil or distillate is caused to be intimately contacted with the oxygen and the solution of alkaliV metal hydroxide, alkali metal monosulphide and alkali metal polysulphide; the sodiumA naphthenate promoting the contact of the oil or distillate with the other reagents so that effective sweetening and removal of corrosive agents from the oil is obtained.

After the intimate mixture in the reacting chamber 3, the now sweetened oil or distillate and reagents pass through the pipe 5 into the settling chamber I where the soap or salt and reagent mixture settle to the bottom to be recirculated through the reacting chamber for treating more sour oil or distillate, the treated and now sweetened oil 0r distillate forms as a supernatant liquid above the mixture of soap or salt and reagent and when the level thereof rises suiciently it flows through the pipe 6 to the second settling chamber 2 for further settling, and nally flows through the pipe 1 to the sweetened oil storage tank 8.

In the examples of the process given above the rate of treatment of the oil or distillate was 3 barrels per minute, that is to say, the oil or distillate was introduced into the mixer 3 through the pipe I4 at a rate of three barrels per minute. The solution drawn from settling chamber I was mixed with the oil or distillate in the proportions of 35% of the solution to 65% of the oil or distillate. Oxygen was introduced at the rate of 2 liters of substantially pure oxygen (99.5% oxygen) per minute, the oxygen being measured at 10 F. and one atmosphere pressure. The amount of oxygen was substantially equivalent to 0.01 cubit foot per each milligram of mercaptan previously determined to be present in the sour naphtha.

The oil or distillate was treated at the temperature or about at the temperature which it had in storage in the metallic storage receptacles exposed to the atmosphere. This is roughly prevailing atmospheric temperatures. Oils and distillates have been successfullytreated according to the present invention at F.,`at which temperature they frequently leave the condensers.

While the treated oil or distillate leaving the settling chamber 2 by means of the pipe 1 will be free of mercaptans, it may, in some instances, be desirable to pass the sweetened oil or distillate through a pipe 1c, having a valve 1d, leading to the bottom of a drum 28 filled with a mixture of two-thirds solid sodium hydroxide in flake form and one-third granular sodium chloride, in order to remove any very small amounts of the treating solution which may be carried along in the treated oil or distillate. The sodium chloride in the sodium hydroxide and sodium chloride mixture retards caking of the sodium hydroxide.

When the treated oil or distillate was passed through the drum 28 before being passed to the storage tank 8, it left the drum free of hydrogen sulphide and alkali metal sulphides, and sweet to the doctor test (i. e., was free of mercaptans) it gave entirely negative corrosion tests and was entirely free of free sulphur; its lamp sulphur decreased from the value of 0.066% to 0.055%; its color was excellent; and its octane number rose from the value of 55.3 to 55.7.

If the sour petroleum distillate does not contain any free sulphur, then the rate of introducing gaseous oxygen into the chamber 3 should be such as to provide, at any instant oi' time, in the chamber 3 a weight of oxygen at least slightly in excess of the weight oi oxygen stoichiometrically required to oxidize, to organic disulphides, all the mercaptan content of the body (volume) of distillate in the chamber 3. If the sour petroleum distillate contains free sulphur, then the rate of introducing gaseous oxygen into the chamber 3 should be such as to provide, at any instant of time, in the chamber 3 -a weight of oxygen at least slightly in excess of the difference between ('a) the weight of oxygen stoichiometrically required to oxidize all the mercaptan content of the body (volume) of distillate in the chamber 3 to organic disulphides as minuend and (b) from 0.3 to 0.5 of the weight of free sulphur in the body (volume) of distillate in chamber 3. In actual practice of the process, when sour petroleum distillates which contain no free sulphur are treated, the amount of oxygen required in chamber 3 may range from 11/2 to 4 times as much as the weight of oxygen stoichiometrically required to oxidize, to organic disulphides, all the mercaptan content in the body (volume) oi' distillate in chamber 3; and in the case of treating sour petroleum distillates which contain free sulphur, the amount of oxygen required in chamber 3 also may range from 11/2 to 4 times the difference between (a) the weight of oxygen stoichiometrically required to oxidize all the mercaptan content of the body (volume) of distillate in the chamber 3 to organic disulphides as minuend and (b) from 0.3 to 0.5 of the weight of free sulphur in the body (volume) of distillate in chamber 3.

Although the above indicated amounts oi oxygen, which are required for the process, can be calculated from the amount of distillate in the chamber 3 at any instant oi' time (or the rate oi ilow of the materials into the chamber) and the analysis of the distillate with respect to mercaptans and free sulphur, it is not absolutely necessary to adopt that procedure. The above amounts of oxygen can very easily be ascertained or selected by adjusting the rate of introduction of gaseous oxygen into the chamber 3 to such a value, by manipulating the valve I8, that the distillate continuously leaves said chamber 3 (or chambers I and 2) free of mercaptans; that is to say, the amount of gaseous oxygen introduced into the chamber is maintained at such a value as to continue the sweetening powers of the solution i'or long periods of time.

If during the course of the practice of my process, the distillate flowing from the chamber 3 (or chambers I and 2) still contains a small content of mercaptans, it is only necessary to increase the rate oi introduction of gaseous oxygen in order to cause the distillate to ilow free of mercaptans from said chamber. After the process has been operated some time with this increased rate of introduction oi oxygen, the rate of introduction can be gradually decreased, and simply adjusted by trial to a new value to continue the ow of mercaptan-free distillate from said chambers.

I'he sodium naphthenate used in each example was prepared by mixing parts of 1.20 specinc gravity, or 19% sodium hydroxide solution with 10 parts of naphthenic acid having a carbon content of six to twenty-four atoms in twenty-tive parts oi' the oil or distillate of the type to be treated. The mixture was thoroughly agitated and then let stand in a quiescent condition until it separated into three distinct layers. 'I'he top layer was the hydrocarbon oil or distillate, the middle layer was the sodium naphthenate and the bottom layerI was the excess of sodium hydroxide solution. The mixing of, the sodium hydroxide, the naphthenic acid andthe hydrocarbon oil or distillate can take place at any temperature above that at whichthe sodium hydoxide would solidify up to a temperature of about F.

The sodium hydroxide was caused to react with naphthenic acid in the presence o! the oil or distillate in order to prevent the formation of an emulsion of the sodium hydroxide and the sodium naphthenate formed as a result .of the reaction, and in order that the sodium naphthenate which was formed would contain a certain amount of the oil or distillate. However, the sodium naphthenate does not necessarily have to be formed in the presence of the oil or distillate. If the oil or distillate is not present during its formation, the emulsion which is formed may be broken by the addition oi a quantity of the oil or distillate, and the resulting mixture would form into separate layers of oil or distillate, sodium naphthenate and excess sodium hydroxide, as when the oil and distillate were present.

'I'he concentration of the-sodium hydroxide solution used in preparing the sodium naphthenate may vary from about 15% to about 30%, but a concentration oi' about 19% is preferred because when an aqueous sodium hydroxide solution oi' that concentration is used the resulting sodium naphthenate will contain approximately 66.67% of oil and about 8% water, both by volume, will be almost transparent, and insoluble both in the oil which forms above it and the sodium hydroxide solution below it. Also the sodium naphthenate produced by using a 19% aqueous solution of sodium hydroxide is more reactive with the octane depressing constituents contained in hydrocarbon oils and distillates of various qualities, especially when used in the treatment of aviation gasoline. That is particularly important as the quantities of antiknock constituents are low in untreated aviation gasoline and it is extremely diilicult, and in some cases impractical, to treat aviation gasoline by the conventional methods without permanently injuring it.

If sodium hydroxide of a concentration higher than about 19% is used the sodium naphthenate which is formed will be more or-less iiocculent and, when subsequently used in the treatment of the oil or distillate will tend to become dispersed in the oil or distillate and be carried out of the settling chamber. If the concentration oi' the sodium hydroxide is lower, the resulting sodium naphthenate tends to go into solution in the excess sodium hydroxide and forms a gel with the hydrocarbon oil or distillate and more sodium hydroxide has to be added to take upV excess water and to salt out the sodium naphthenate. In other words, if a sodium hydroxide solution oi' a concentration other than about 19% is used it subsequently will be necessary either to add water or anhydrous sodium hydroxide, depending upon whether the concentration was above or below about 19%, in order that the formed sodium naphthenate will be in its most; eil'ective condition to promote contact between the hydrocarbon oil or distillate being treated and the other conditioning reagents, and

asaacie to bring about a sweetening of the oil and the removal of corrosive agents therefrom.

The balance between the hydrocarbon oil or distillate and the water present in the sodium naphthenate which is formed is important and depends on the concentration of the sodium hydroxide solution which is used. The permissible amount of water which may be present in the sodium naphthenate is from about 6% to about 10% although about 8% is preferred.

The amount of hydrocarbon oil/.or distillate which the sodium naphthenate should contain may vary from about 60% to about '10% although about 66.67% is preferred. As indicated above, the use of an aqueous sodium hydroxide solution of about 19% concentration will produce sodium naphthenate containing about 8% water and about 66.67% hydrocarbon oil or distillate. If a-solution of sodium hydroxide of lower concentration, for example, a concentration of about is used the resulting sodium naphthenate will contain about 12% water and less hydrocarpon oil or distillate, the additional water displacing or driving out a part of the hydrocarbon oil or distillate. On the other hand, if the concentration of the sodium hydroxide is higher, for example, about or 30%, the resulting sodium naphthenate will contain 1% or less of water and will be ilocculent and disperse throughout the oil. In its occulent state the sodium naphthenate has less wetting properties and accordingly does not as well promote contact between the hydrocarbon oil or distillate and the other reagents and does not promote those/reactions which cause the hydrocarbon oil to be sweetened and the corrosive agents removed.

While specific reference has herein been made to sodium naphthenate for promoting the sweetening of the hydrocarbon oil or distillate and for promoting the removal of 'corrosive agents, it is to be understood that soaps or salts other than sodium naphthenate may beA used for promoting the sweetening of the oil. The only essential seems to be that the soap or salt must be of a metal which forms a soluble sulphide. If a soap or salt of a metal which forms an insoluble sulphide is used, it will react with sulphur present or the sodium sulphides present to form insoluble sulphides which will precipitate out and no sweetening of the oil will be obtained. I have found that soaps or salts formed by alkali metal bases and any of the following acids are effective in promoting the sweetening of hydrocarbon oils or distillates: Gluconic, ptoluenesulfonic, sulfanilic, adipic, maleic, anthranilic, silicofiuoric, arsenic, arsenous, glycocoll, succinic, phthalic, salicylic, silicio, pyrophosphoric, benzoic, orthophosphoric, thiocyanic, citric, stearic, oleic, abietic and naphthenic.

Likewise, it is not necessary that sodium naphthenate be used in order to promote those reactions which cause the removal of corrosive agents present in the oil being treated, a1- though it does not appear that every soap or salt of a metal which forms soluble sulphides is effective in promoting the removal of corrosive agents. However, I have found that soaps or salts formed from alkali metal bases and sulfanilic, arsenic, glycocoll, succinicl thiocyanic and naphthenic acids were effective both in promoting the sweetening of the hydrocarbon oil or distillate and vin the removal of corrosive agents therefrom.

In each of the examples given, the soap or salt was first formed and added to the treating solution. However, it will not always be necessary to rst form the soap or salt and add it as such to the treating solution. If'the hydrocarbon oil or distillate to be treated contains an acid which will react with the sodium hydroxide in the treating drums to form a soap or salt, the metal of whichv forms a soluble sulphide, as, f or example, when the oil or distillate is derived from a naphthenlc base crude and contains naphthenic acid, it will not be necessary to first form the soap or salt and add it to the other reagent or reagents. In such a case it will be sufcient if the oil and the sodium hydroxide or the oil and the sodium hydroxide and other reagents are circulated through the mixer 3 and settling chamber 4 I untll a suflicient amount of the soap or salt has been formed, -by reaction between the sodium hydroxide and the acid content of the oil or distillate, to promote the sweetening of the oil or distillate, or both sweetening of the oil or/ distillate and the removal of corrosive agents. However, even in such cases it is desirable to rst form the soap or salt and add it to the other reagent or reagents, due to the length of time it may take to form a sumcient amount of the soap or salt to effectively promote the sweetening of the oil or `distillatnf'ButI regardless of how the soap or salt'isformed. the essential thing is that it, like the uncombined oxygen, should be present when the oil or distillate is contacted with the solution containing the sodium hydroxida, the sodium monosulphide and the sodium polysulphide.

The sodium naphthenate also preferably is first formed and then added to the solution of sodium hydroxide containing the sodium monosulphide and sodium polysulphide, because if the naphthenic acid was added to the solution of sodium hydroxide containing the sodium monosulphide and sodium polysulphide, hydrogen sulphide would be liberated which would react with the excess NaOH and change the concentration of the solution to an extent such that a stable emulsion would be formed which is insoluble in the oil or distillateand is not readily broken to separate the sodium naphthenate from the solution of sodium monosulphide and sodium polysulphide in sodium hydroxide.

The treatment of the-"oil or distillate may be carried out at any temperature which normally would exist, or at any temperature upto about F. The temperature at which the oil or distillate is treated should not be permitted torise above about 120 F. because. it has been found that above about that temperature the sodium naphthenate or other soap or salt is less effective in promoting the sweetening of the oil or distillate and the removal of corrosive agents therefrom, probably due to the formation of undesirable polysulphides which have a very low ail'inity for free sulphur. At any rate, when sodium naphthenate is used above about that temperature the oil or distillate does not settle bright and clear and sulphur is not removed. The pressure under which the treatment takes place is immaterial. It may be at atmospheric or higher or lowerfpressure.

The relative amounts of the sodium hydroxide, sodium sulphide, sodium polysulphide, and sodium naphthenate or other soap or salt used in the treatment of the oil or distillate should be held in relatively narrow limits if the best results are to be obtained.

Hydrocarbon oil distllates obtained from straight run distillation of petroleum, or from distillations following cracking of petroleum distillates or residues, can be treated according to the process oi' the present invention.

Instead of the water solution described in the above example, which is prepared from sodium hydroxide, sodium monosulphide and sulphur, I may use a water solution prepared in like manner but in which potassium hydroxide and potassium monosulphide are substituted in whole or in part respectively for the sodium hydroxide and sodium monosulphide.

While the process of the present invention has been described in considerable detail and two examples of a preferred method of carrying out the invention have been given, it is to be understood that such detailed description is by way of exemplication and that various changes within the scope of the appended claims may be made without departing from the invention or losing any of the advantages thereof.

This application is in part a continuation of my application Serial No. 332,837, illed May 1, 1940, for Sweetening sour hydrocarbon oils.

What is claimed is:

l. The process of treating hydrocarbon oils by converting the mercaptans in the oil into sulphides not higher in sulphur content than disulphides which comprises contacting the oil in the liquid phase, at a temperature not substantially exceeding 120 F. and in the presence of added extraneous gaseous oxygen and a salt of a metal which forms water soluble sulphides, with a solution containing an alkali metal hydroxide, an alkali metal monosulphide and an alkali metal polysulphide.

2. The process of treating hydrocarbon oils by converting the mercaptans in the oil into sulphides not higher in sulphur content than disulphides which comprises contacting the oil in the liquid phase, at a temperature not substantially exceeding 120 F. and in the presence of added extraneous gaseous oxygen and a salt oi' a metal which forms water soluble sulphides, with a solution containing an alkali metal hydroxide, an alkali metal monosulphide and an alkali metal polysulphide, the sum of the uslphur content of the alkali metal monosulphide and the alkali metal polysulphide corresponding to that of mixtures oi' alkali metal monosulphide and alkali metal disulphide.

3. The process of treating hydrocarbon oils by converting the mercaptans in the oil into sulphides not higher in sulphur content than disulphides which comprises contacting the oil in the liquid phase, at a temperature not substantially exceeding 120 F. and in the presence of added extraneous gaseous oxygen and a salt of a metal which forms water soluble sulphides, with a solution containing an alkali metal hydroxide, an alkali metal monosulphide and an alkali metal polysulphide, the amount of oxygen present during said contacting of the oil or distillate being in excess of that required stoichiometrically for oxidizing all the mercaptan content of the body of oil or distillate to organic disulphides.

4. The process of treating hydrocarbon oils by converting the mercaptans in the oil into sulphides not higher in sulphur content than disulphides which'comprises contacting the oil in the liquid phase, at a temperature not substantially exceeding 120 F. and in the presence of added extraneous gaseous oxygen and a salt of a metal which forms water soluble sulphides, with a solution containing an alkali metal hydroxide,

an alkali metal monosulphide andan alkali metal polysulphide, said salt containing about 8% o! water. 1

5. The process of treating hydrocarbon oils by converting the mercaptans in the oil into sulphides not higher in sulphur content than disulphides which comprises contacting the oil in the liquid phase, at a temperature not substantially exceeding F. and in the presence of added extraneous gaseous oxygen and a salt of a metal which forms Water soluble sulphides, which salt contains from about 6% to about 10% oi' water, with a solution containing an alkali metal hydroxide, an alkali metal monosulphide and an alkali metal polysulphide.

6. The process oi' treating hydrocarbon oils by converting the mercaptans in the oil into sulphides not higher in sulphur content than disulphides which comprises contacting the oil in the liquid phase, at a temperature not substantially exceeding-l20 F. and in the presence of added extraneous gaseous oxygen and a salt o! a metal which forms water soluble sulphides, which salt contains from about 6% to about 10% of Water, with a solution containing an alkali metal hydroxide, an alkali metal monosulphide and an alkali metal polysulphide, the sum of the sulphur content of the alkali metal monosulphide and the alkali metal polysulphide corresponding to that of mixtures of alkali metal monosulphide and alkali metal disulphide and the amount of oxygen present during said contacting of the oil being in excess of that required stoichiometrically for oxidizing all the mercaptan content of the body o! oil to organic disulphides.

7. The process of treating hydrocarbon oils by converting the mercaptans in the oil into sulphides not higher in sulphur content than disulphides which comprises conducting a stream or the oil in the liquid phase, and at a temperature not substantially exceeding 120 F. into mixing means, introducing oxygen into the stream o1' oil ilowing to the mixing means. introducing into the mixing means a salt of a metal which forms water soluble sulphides and an aqueous solution containing an alkali metal hydroxide, an alkali metal monosulphide andan alkali metal polysulphide, the sum of the sulphur content oi the alkali metal monosulphide and the alkali metal polysulphide corresponding to that of mixtures of alkali metal monosulphide and alkali metal disulphide, and the amount of oxygen being in excess of the difference between (a) the amount of oxygen stoichiometrically required to oxidize all the mercaptan content of the oil in the mixing means to organic disulphides as minuend and (b) from 0.3 to 0.5 of the amount of any free sulphur in the oil in the mixing means, and intimately mixing the contents of the mixing means so that mercaptans in the oil are converted into sulphides not higher in sulphur content than disulphides.

8. The process of treating hydrocarbon oils by converting the mercaptans in the oil into sulphides not higher in sulphur content than disulphides which comprises intimately mixing a body of the oil in the liquid phase, and at a temperature not substantially exceeding 120 F. with a solution containing an alkali metal hydroxide, an alkali metal monosulphide and an alkali metal polysulphide, the sum of the sulphur content of the alkali metal monosulphide and the alkali metal polysulphide corresponding to mixtures of alkali metal monosulphide and alkali metal disulphide, said mixing taking place in the presence of a salt of a metal which forms water soluble sulphides and added extraneous gaseous oxygen in an amount in excess of that required stoichiometrically for oxidizing all the mercaptan content of the oil to organic disulphides.

9. The process of treating hydrocarbon oils by converting the mercaptans in the oil into sulphides not higher in sulphur content than disulphides which comprises intimately mixing a body of the oil in the liquid phase, and at a temperature not substantially exceeding 120 F. with a solution containing an alkali metal hydroxide, an alkali metal monosulphide and an alkali metal polysulphide, the sum of the sulphur content of the alkali metal monosulphide and the alkali metal polysulphide corresponding to mixtures of alkali metal monosulphide and alkali metal disulphide, said mixing taking place in the presence of a salt of a metal which forms water soluble sulphides and added extraneous gaseous oxygen, withdrawing the mixture formed in said mixing means as fast as the chamber is charged with components to form said mixture, and regulating the amount of oxygen present so that the mercaptan content of the oil is oxidized and the oil withdrawn from the mixing means is substantially free of mercaptans.

10. The process of treating hydrocarbon oils by converting the mercaptans in the oil into sulphides not higher in sulphur content than disulphides which comprises intimately mixing the oil, in the liquid phase and at a temperature not substantially exceeding 120 F. in the presence of added extraneous gaseous oxygen and a salt of a metal which forms water soluble sulphides, with a solution containing an alkali metal hydroxide, an alkali metal monosulphide and an alkali metal polysulphide, the amount of oxygen present during such mixing being sufficient to oxidize all of the mercaptan content of the oil, separating the hydrocarbon oil and the solution from each other after such mixing, and returning the separattd solution for mixing with further amounts of oi 11. The process of treating hydrocarbon oil by converting the mercaptans in the oil into sulphides not higher in sulphur content than disulphides which comprises intimately mixing the oil in the liquid phase and at a temperature not substantially exceeding 120 F., in the presence of added extraneous gaseous oxygen and sodium naphthenate, with a solution containing sodium hydroxide, sodium monosulphide and sodium polysulphide.

12. The process of treating hydrocarbon oil by converting the mercaptans in the oil into sulphides not higher in sulphur content than disulphides which comprises intimately mixing the oil in the liquid phase and at a, temperature not exceeding about 120 F. and in the presence of added extraneous gaseous oxygen and sodium naphthenate, with a solution containing sodium hydroxide, sodium monosulphide and sodium polysulphide, the sum of the sulphur content of the alkali metal monosulphide and the alkali metal polysulphide corresponding to that of mixtures of alkali metal monosulphide and alkali metal disulphide.

13. The process of treating hydrocarbon oil by converting the mercaptans in the oil into sulphides not higher in sulphur content than disulphides Which comprises intimately mixing the oil in the liquid phase at a temperature not exceeding about 120 F. and in the presence of added extraneous gaseous oxygen and sodium naphthenate containing from about 6% to about 10% of water, with a solution containing sodium hydroxide, sodium monosulphide and sodium polysulphide, the sum of the sulphur content of the alkali metal monosulphide and the alkali metal polysulphide corresponding to that of mixtures of alkali metal monosulphide and alkali metal disulphide, and the amount of oxygen present during said mixing of the oil being in excess of that required stoichiometrically for oxidizing all the mercaptan content of the body of oil to organic disulphide.

14. The process of treating hydrocarbon oils by converting the mercaptans in the oil into sulphides not higher in sulphur content than disulphides which comprises contacting the oil in the liquid phase, at a temperature not substantially exceeding 120 F. and in the presence of added extraneous gaseous oxygen and a salt of a metal which forms Water soluble sulphides, with a solution containing an alkali metal hydroxide, an alkali metal monosulphide and an alkali metal polysulphide, separating the oil or distillate from said solution, and contacting the separated oil with solid sodium hydroxide.

15. The process of treating hydrocarbon oils by converting the mercaptans in the oil into sulphides not higher in sulphur content than disulphides which comprises contacting the oil in the liquid phase and at a temperature not exceeding about 120 F. and in the presence of added extraneous gaseous oxygen and a salt of a metal which forms soluble sulphides, with a solution containing an alkali metal hydroxide, an alkali metal monosulphide and an alkali metal polysulphide, the amount of oxygen present during said contacting of the oil or distillate being in excess of that required stoichiometrically for oxidizing all the mercaptan content yof the body of oil to organic disulphides, separating the oil from said solution, and contacting the sepa.-

CHARLES O. HOOVER. 

